Msk Dermatology · Year 2 · from Msk Dermatology

Case 4: Scabies

Patient Presentation

Demographics: 28-year-old female

Chief Complaint: Intense itching worse at night for 3 weeks

History of Present Illness: The patient has had progressive, severe itching for 3 weeks. The itching is worse at night and interferes with sleep. She noticed small bumps on her wrists, between her fingers, and around her waist. Her boyfriend has developed similar symptoms. She works at a nursing home where several residents have been diagnosed with scabies.

Physical Examination:

  • Skin:
  • Erythematous papules on wrists, finger web spaces, and waistline
  • Linear, thread-like burrows visible between fingers
  • Excoriations from scratching
  • No face or scalp involvement
  • Distribution: Wrists, web spaces, axillae, waist, genitalia

Workup and Results

Skin Scraping:

  • Mineral oil preparation: Sarcoptes scabiei mite, eggs, and fecal pellets (scybala) visualized

Clinical Image

Clinical photograph showing scabies with characteristic linear burrows in the web spaces between fingers, along with erythematous papules. Burrows are pathognomonic for scabies infestation.

Diagnosis

Scabies (Sarcoptes scabiei infestation)

Features:

  • Intense nocturnal pruritus
  • Characteristic distribution (web spaces, wrists, waist, genitalia)
  • Pathognomonic burrows
  • Close contact transmission

Discussion

This case illustrates scabies:

  • Mite Infestation: The lecture identifies scabies as caused by the mite Sarcoptes scabiei, which burrows into the stratum corneum.
  • Burrows as Pathognomonic: The lecture describes burrows as the pathognomonic finding in scabies. They represent the tunnels where female mites lay eggs.
  • Permethrin First-Line: The lecture states that topical permethrin 5% is the first-line treatment for scabies. It is applied from neck to toes and left on for 8-14 hours.
  • Norwegian (Crusted) Scabies: The lecture notes that Norwegian (crusted) scabies occurs in immunocompromised patients and is highly contagious due to massive mite burden.

Treatment Plan

  1. Topical Permethrin 5% (First-Line):
  • Apply to entire body from neck down
  • Include between fingers, under nails, genitalia
  • Leave on for 8-14 hours, then wash off
  • Repeat in 1 week
  1. Household Contacts:
  • Treat all close contacts simultaneously
  • Even if asymptomatic
  1. Environmental Measures:
  • Wash all clothing, towels, bedding in hot water
  • Items that cannot be washed: seal in plastic bag for 3 days
  • Vacuum furniture and carpets
  1. Pruritus Management:
  • Antihistamines (diphenhydramine, hydroxyzine)
  • Pruritus may persist for 2-4 weeks after successful treatment (due to dead mite antigens)
  1. Alternative Treatment:
  • Oral ivermectin 200 mcg/kg (repeat in 2 weeks)
  • Useful for outbreaks, crusted scabies, or treatment failure

Teaching Points

  1. Scabies is caused by the mite Sarcoptes scabiei
  2. Burrows are pathognomonic
  3. Permethrin 5% cream is first-line treatment
  4. Treat all close contacts simultaneously
  5. Norwegian (crusted) scabies is seen in immunocompromised patients

Image Reference

For visual reference of skin infection concepts, see:

Learning Points

  1. Necrotizing Fasciitis: Pain out of proportion is the hallmark; urgent surgical debridement is critical
  1. Herpes Zoster: Dermatomal, unilateral; antiviral within 72 hours; Tzanck shows multinucleated giant cells
  1. Tinea Capitis: Requires oral antifungals; KOH shows hyphae; Microsporum fluoresces on Wood lamp
  1. Scabies: Burrows are pathognomonic; permethrin 5% is first-line; treat all contacts

All cases for this lecture as Markdown